[.a.t.]

Is there a tool to repair mangled lens accessory threads? I'm not asking about dent repairs. I know there are vises and DIY methods for fixing dents.

Rather, I'm wondering about threads such as these:




I've been searching for thread "repair" and "restore" tools, but there are many varieties and I'm just not sure what I'm actually looking for.

Any guidance?

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Last edited by .a.t.; 11-13-2021 at 12:02 PM. Reason: revised title

[marcusBMG]

IMO without a tap or proper thread cutting tool, the one thing yo can do is use an appropriate sized screwdriver or knife blade tip and scrape it along the thread to clean off all the rough bits. At least thats what I do. As long as the thread is essentially undistorted that will do the trick.

[.a.t.]

Thanks for the quick reply, marcus!

Yes, I tried a small screwdriver blade before I took the above photo. So I may have already improved the threads a bit. As they are now, I can force a lens hood on, but it's not easy.
I was hoping to clean them up as well as make them functional again.

If no one knows of a simple tool - say costing no more than $50 - I'll try the screwdriver blade again.
One problem with that method is I don't have a good enough magnifying tool to really see what I'm doing.
Someday I'll probably start a thread about that topic, too...

[crazy4oldcars]

Look for a micro file set. I got mine from harbor freight. Light strokes and magnification are your friends. Just don't get in a hurry. (I don't want to talk about it...)

[Parallax]

If the area is a relatively small portion of the circumference, as it appears to be in the photo, just file or cut that down to the base level.

[MikeMcE]

Yes there’s a tool for that.
I can’t put my fingers on it now, but all it is for practical purposes is a tap that has two flutes 180 degrees apart , mounted in a handle. If the ring has been rounded again you slide this in the threads it then cuts the spots out. The rings look rough, but usually hold a filter.

This is what snappy sells on the truck:

https://shop.snapon.com/product/Thread-Restoring-Files/Thread-Restorer-File-...oint)/TFM7530B


Hang up and DRIVE!

[35mmfilmfan]

Would a pair of dividers from a school geometry set be fine enough and sturdy enough to do the trick ?

[marcusBMG]

I hadn't come across those thread restorer files before - learn st new... However they clearly aren't so good for internal threads. To improve the stripped eyepiece thread on a scope I used a tap of the appropriate pitch held against the thread and moved sideways.

[Not a Number]

There was another thread on this subject that showed a number of "files" as in MikeMcE's post. Maybe posted by @stevebrot ? You just run it around the inside diameter in a semi-circular stirring motion.

[Bob 256]

A Tap (with the same thread pitch) mounted in a holder can be used but with care. You use it as Not a Number mentioned with low pressure and it will scour the threads (overlap the good threads and let them guide its path). It works better on plastic than aluminum but with a few passes, you should see some improvement though it will remove material and not straighten it much.

[marcusBMG]

Just been reading about thread chaser tools/taps

Thread chasing: Restoring male or female fastener threads | 2014-12-17 | Auto Service Professional

[.a.t.]

Thanks to all for your replies and suggestions. I think you've helped point me in the right direction.

If the area is a relatively small portion of the circumference, as it appears to be in the photo, just file or cut that down to the base level.

Yes, the damage is limited to what's in the photo. And for that basket case lens, I'd be willing to try your suggestion as an experiment. But I have another lens with the same problem with which I'd like to be more gentle.

Would a pair of dividers from a school geometry set be fine enough and sturdy enough to do the trick ?

If I had a pair, I'd give it a try. But I think a dedicated tool would probably be more effective.


@crazy4oldcars & @MikeMcE : I'm going to buy a file as you suggested.


Also, this tool looks to be a possibility:
McMaster-Carr
It appears they don't have a metric .75 pitch die, but I believe the 24 TPI die would be equivalent.

[MikeMcE]

A trick I didn’t mention is after it’s all done and things fit on, a wipe with a sharpie will blacken it.


Hang up and DRIVE!

[.a.t.]

I hadn't come across those thread restorer files before - learn st new... However they clearly aren't so good for internal threads...

Yes, I've been looking at those thread files again and I'm having trouble visualizing how they'd work on internal threads.
I might just go ahead and try the tool I linked to in my previous post instead.

A trick I didn’t mention is after it’s all done and things fit on, a wipe with a sharpie will blacken it.

Thanks for the tip. I've used Birchwood Casey Aluminum Black for touch ups and it works, too:
Aluminum?Black Metal Finish, 3 fl. oz. Bottle - Birchwood Casey

[DonV]

Search for "riffler" a type of small file.
Short cutting area, curved on a longer bar- usually have two ends; can be triangular, rounded, or square; of course you would need the triangular type.